A secondary battery having easy applicability depending on a product group and electrical characteristics such as high energy density has been generally applied to an electric vehicle (EV) driven by an electrical driving source and a hybrid vehicle (HV) which are driven by an electrical driving source, an energy storage system (ESS) or an uninterruptible power supply (UPS) system which uses a medium-large size battery used for a household or industrial purpose, and the like, as well as portable devices.
The secondary battery may surprisingly reduce the use of fossil fuel and does not generate by-products due to the use of energy at all and therefore has received attention as a new energy source for enhancing environmentally-friendly characteristics and energy efficiency.
When the secondary battery is implemented as a battery for a portable terminal, and the like, the secondary battery may not necessarily be like that, but the battery applied to the electric vehicle, or the energy storage source as described above is generally used in a form in which a plurality of unit secondary cells is collected and thus has high suitability for high-capacity environment.
When the battery, in particular, a plurality of secondary batteries repeatedly carries out charging and discharging, it is necessary to manage the battery by efficiently controlling the charging and discharging of the battery so as to appropriately maintain the operation state and performance of the battery.
To this end, a battery management system (BMS) to manage the state and performance of the battery is provided. The BMS serves to detect the current, voltage, temperature, and the like of the battery, calculate a state of charge (SOC), equalize a cell voltage, detect and determine whether the battery is swelled, based on the detected current, voltage, and temperature of the battery, and cut-off a charging and discharging current by irreversibly disconnecting a line so as to protect a battery pack when abnormality of the battery is sensed.
Generally, the battery itself in the battery pack is vulnerable to safety, and even though the battery pack is configured to include a safety apparatus using various electronic components, safety accidents such as ignition, fuming, and explosion due to the problem of the battery pack occur.
Further, devices using the battery may be exposed to problems such as impact, overheating, overcharging, and a short circuit due to use environment and a behavior of a user, and under such circumstances, the battery may have a problem in stability and may cause ignition or explosion. Prior to the occurrence of the safety accidents, the battery involves a swelling phenomenon that the battery is swelled, and the explosion or the ignition of the battery may be sensed in advance based on the swelling phenomenon.
Therefore, a necessity to sense the swelling phenomenon of the battery has emerged, and therefore various sensing or detecting apparatuses have been devised.
In order for the apparatus for sensing swelling of a battery according to the related art to sense the swelling of the battery, a housing of the battery is provided with a pressure sensor, a temperature sensor, or the like, which are inefficient in an economical aspect and has a relatively complicated structure, such that the apparatus for sensing swelling of a battery may be expensive and may have an increased volume due to an additional space required for installation. Further, the sensors may be broken under high temperature and high pressure.
Therefore, the present inventors have contrived the present invention to solve the above-mentioned problems.